In brief, the gag dub by ADV was approved by the Japanese company and done with their consent. Anime purists find this tantamount to the most heinous sacrilege but I find the dub very amusing!
It is true that they throw in many many obscure cultural references, most of which will be lost with time, dating the English dub. But the dubbing is done so well. The wisecracks and jokes never stop and if you just enjoy it, its like South Park or something like that. The kids do swear like sailors and this gets worse as the series goes on, so if swearing wisecracks aren't your cup of tea, you might want to avoid this tea pot.
The English dub starts out slow and stays pretty much faithful to the original Japanese plots but takes off around Episode 5 or 6. I find that the quality really starts to drop off in the last three or four episodes though. In these last few episodes, the ad-libbing seems to rely only on stringing together obscenities and seeing how many times you can drop the F-bomb. Maybe they were running out of time. Maybe they were drinking and were totally potchkied by the end of the run.
In total though, the English Dub is humorous and light, something good to watch after a hard day's work to make you laugh. For me, I find the series has a very high repeat-viewing value. Its not Miyazaki but I would definitely give this show at least three stars and a hearty thumbs up for those wanting some good light entertainment.